In order to rationalize to some extent the casting of concrete floors, it has been proposed to use concrete beams as combined stop-ends and screed guides for concrete smoothing devices, the beams being embedded in the floor with the upwardly facing surfaces of the beams flush with the resultant floor surface. This eliminates the task of stripping the formwork, and hence the various spans can be cast in sequence, since adjacent spans can be cast simultaneously.
Among other things, however, these known methods do not solve the problem of providing non-contacting or isolated areas around pillars, floor-drains and the like, in a ready and simple fashion. Pillars which are not sufficiently isolated from the floor as the floor is cast, will ultimately be in load-transferring contact therewith, inter alia as a result of shrinkage stresses occurring in the concrete. This means, among other things, that when a pillar is subjected to heavy loads, which tends to cause the pillar to settle, the floor will also be subjected to stress, causing cracks to form. In addition, the pillar itself obtains therearound an area of concentrated stresses, which can readily cause the pillar to crack.
These methods used today for isolating pillars from the surrounding floor either do not provide a satisfactory result or require a large amount of additional work. Moreover, they require the floor to be cast in a plurality of stages.
The known concrete beams used as combined stop-ends and screed guides for co-action with concrete-smoothing devices are also encumbered with certain additional disadvantages. For example, they do not prevent relative movement between adjacent floor sections in the longitudinal direction of the beams. Furthermore, the webs of the beams are provided with open holes, through which reinforcing rods or the like can be passed. In order to enable the reinforcement to be compactly formed in a selective fashion, the webs of respective beams must be provided with a large number of holes, of which only a relatively small number are used in each individual case. This results in copious leakage of concrete through the beams, which is highly unsatisfactory when the beam is also to serve as a stop-end.